Field of the Invention
The present invention relates to a hybrid wireless power transmitting apparatus and a method for the system.
Related Art
The advance of wireless communication technology has brought a ubiquitous information environment where people can get any information that they want at any time and any place. However, most of communication information devices still rely on batteries, and use of the devices is being limited since they receive power via power lines.
Therefore, the wireless information network environment cannot be fully utilized unless the problem related to device power is solved.
To solve the problem, various methods for wireless power transmission are under development, typical examples of which include a microwave receiving method, a method based on magnetic induction utilizing magnetic field, or a method based on magnetic resonance due to energy conversion between magnetic and electric fields.
The microwave receiving method has an advantage that power can be transmitted a long distance since microwaves can be radiated into the air through an antenna, but efficiency of power transmission is restricted due to considerable radiation loss in the air.
On the other hand, the magnetic induction method makes use of magnetic energy coupling due to primary and secondary coils, utilizing a transmitting coil as a transmitter and the secondary coil as a receiver. The magnetic induction exhibits a high efficiency of power transmission. However, it is also limited because the first and the second coil have to be located within a short distance of a few millimeters, and efficiency of power transmission is rapidly changed according to the arrangement of the first and the second coil.
Due to these reasons, a method based on magnetic resonance is getting more attention these days, which is similar to the method based on magnetic induction, but transmits power in the form of magnetic energy by concentrating the energy at a specific resonant frequency determined by coil-type inductors (L) and capacitors (C). The magnetic resonance method is advantageous since it can transmit relatively large energy a long distance of up to a few meters, but this also requires high quality resonance factor. In other words, the magnetic resonance method is disadvantageous in that efficiency of power transmission changes rapidly according to how well impedance matching or resonant frequency matching is performed.
Accordingly, in the technical field to which the present invention belongs, taking into account the fact that a method based on magnetic induction is more advantageous if the distance between transmitting and receiving coils is short while a method based on magnetic resonance is more advantageous when the distance between the transmitting and receiving coils is large, a hybrid wireless power transmission system is being proposed which utilizes advantages of both of the magnetic induction method and the magnetic resonance method.